MultiBond layered composite material: Hard and tough

Damascus steel knives offer impressive hardness and impact toughness. Hoesch Hohenlimburg GmbH has now adapted this centuries-old craft to industrial-scale production for the first time – and at the same time improved both the strength and impact toughness of the knives. The multi-phase steel MultiBond has made this possible. In addition to kitchen knives, the company also sees great market potential for MultiBond above all in the area of cutting tools for harvesting machinery. Hoesch Hohenlimburg is presenting the new steel at the EuroBLECH trade fair in Hanover from October 21 to 25, 2014 in hall 17, booth E 33.

Good knives need to be sharp – and remain that way for a long time. That’s why the material needs to be as hard as possible. However, the harder the steel, the more brittle it becomes. This is a difficult balance to strike – a knife must not break when it is dropped. Damascus steel offers an answer: hard, darker layers alternate with soft, lighter layers. While the hard layers ensure good strength, the ductile areas of the knife ensure the desired impact toughness. The alternating layers also give the knife a unique appearance.

To date, such Damascus steel blades have been produced from 200-kilogram billets in smaller rolling mills. Hoesch Hohenlimburg has now adapted the manufacture of these Damascus steels to industrial scale – and thereby significantly reduced production costs for the cutting tools. “Instead of 200-kilogram billets, we are producing the knives from slabs weighing seven tons. That’s unique throughout the world,” says Dr. Andreas Tomitz from Hoesch Hohenlimburg.

The starting material is the layered composite MultiBond, which Hoesch Hohenlimburg GmbH has adapted to the property profile required by cutting tools in a joint development project with a kitchen equipment manufacturer. Now the high-quality Damascus steel knives are to be launched on the market. The lower costs are not the only advantage MultiBond steel offers customers: The knives also last significantly longer than current Damascus steel knives and exhibit extremely high fracture toughness.

Cutters for harvesting machinery: More durable and safer

However, the company does not expect the biggest market share to come from kitchen knives, but rather industrial blades such as those used in harvesting machinery. “We expect sales of layered composite materials for this application to increase roughly tenfold by 2020,” says Dr. Tomitz. To date, the cutters in combine harvesters have been made from single-phase steels. However, the strength of these blades is limited – and consequently so is their durability. Increasing strength would make the material too brittle and potentially cause it to shatter if the blade were to hit a stone. This is not the case with cutters made from MultiBond: Durability is doubled and impact toughness significantly improved.

Customized property profiles

Which materials Hoesch Hohenlimburg uses for the MultiBond steel depends on the application. “We adapt the property profile of MultiBond to individual customer wishes,” explains Dr. Tomitz. Firstly, the two materials are joined to produce a slab which already exhibits the typical MultiBond layer structure. Together with ThyssenKrupp Steel Europe in Duisburg, Hoesch Hohenlimburg has optimized the production of these slabs. In a subsequent step, the slab is rolled at around 1,200 degrees Celsius. The layers become inseparably welded together – and give the steel its elegant, unmistakable Damascus look. It is produced in the form of narrow strip: This premium product has close thickness tolerances and exhibits homogenous properties along the entire strip length.

Visit us at EuroBLECH 2014 in Hanover from October 21 to 25, hall 17, booth E 33.